1、Designation: D 4425 97 (Reapproved 2002)An American National StandardStandard Test Method forOil Separation from Lubricating Grease by Centrifuging(Koppers Method)1This standard is issued under the fixed designation D 4425; the number immediately following the designation indicates the year oforigin
2、al adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for determiningthe tenden
3、cy of lubricating grease to separate oil when sub-jected to high centrifugal forces.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and
4、 determine the applica-bility of regulatory limitations prior to use.1.3 The values stated in SI units are to be regarded as thestandard.2. Referenced Documents2.1 ASTM Standards:D 217 Test Methods for Cone Penetration of LubricatingGrease23. Terminology3.1 Definitions:3.1.1 lubricating grease, na s
5、emi-fluid to solid product ofa thickener in a liquid lubricant.3.1.1.1 DiscussionThe dispersion of the thickener forms atwo-phase system and immobilizes the liquid lubricant bysurface tension and other physical forces. Other ingredients arecommonly included to impart special properties. D 2173.1.2 t
6、hickener, nin lubricating grease, a substance com-posed of finely-divided particles dispersed in a liquid to formthe productss structure.3.1.2.1 DiscussionThickeners can be fibers (such as vari-ous metallic soaps) or plates or spheres (such as certainnon-soap thickeners), which are insoluble or, at
7、most, only veryslightly soluble in the liquid lubricant. The general require-ments are that the solid particles be extremely small, uniformlydispersed, and capable of forming a relatively stable, gel-likestructure with the liquid lubricant.3.2 Symbols:a = distance from top of grease surface to tube
8、mouth(mm).b = height of liquid column in an inverted test tube(mm).d = test tube inside diameter (mm).H = accumulated test time at a given reading (h).K36 = resistance to centrifugal separation (V/H).r = measured at the maximum radius of rotation (mm).rpm = rotational speed (r/min).V = volume of sep
9、arated oil, as a percentage of theoriginal grease volume (%).Vg= grease volume in a test tube (cm3).Vo= volume of separated oil (cm3).Vt= test tube total volume (cm3).A = angle of rotor, between the test tube axis and axis ofrotation (degrees).v = rotational speed (rad/s).G = relative centrifugal ac
10、celeration.The relative effect of centrifugal forces, when related to thegravitational standard acceleration (9.81 m/s2), is noted withthe symbol G. It can be calculated as follows:G 5 1.02 3 10243 r 3v2, (1)orG 5 1.12 3 10263 r 3 rpm2(2)4. Summary of Test Method4.1 Pairs of centrifuge tubes are cha
11、rged with greasesamples and are placed in the centrifuge. The grease samplesare subjected to a centrifugal force equivalent to a G value of36 000, at 50C 6 1C, for specific periods of time. Theresistance of the grease to separate the oil is then defined as aratio of the percent of oil separated to t
12、he total number of hoursof testing.5. Significance and Use5.1 This test method is useful in evaluating the degree towhich a grease would separate into fluid and solid componentswhen subjected to high centrifugal forces. Flexible shaftcouplings, universal joints, and rolling element thrust bearings1T
13、his test method is under the jurisdiction of Committee D02 on PetroleumProducts and is the direct responsibility of Subcommittee D02.G on LubricatingGrease.Current edition approved June 10, 1997. Published October 1997. Originallypublished as D 4425 84. Last previous edition D 4425 90.2Annual Book o
14、f ASTM Standards, Vol 05.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.are examples of machinery which subject lubricating greases tolarge and prolonged centrifugal forces. This test method hasbeen found to give results that cor
15、relate well with results fromactual service. The test method may be run at other conditionswith agreement between parties but the precision noted in thistest method will no longer apply.36. Apparatus6.1 High-Speed Centrifuge capable of developing a G valueof 36 000. Mount the unit on a flat level su
16、rface to allowunrestricted air flow to the motor. This is essential for longmotor life. The centrifuge should be equipped with:6.1.1 Fixed Angle Rotor, multiple place, which can sustaina G value of 36 000.6.1.2 Thermometer, preferably of a dial type, installed sothat the temperature in the vicinity
17、(5 to 15 mm) of the rotorcan be measured. (For Sorvall centrifuge, see Fig. 1.)6.1.3 Air Choke, installed at the air inlet of the centrifugechamber (for Sorvall centrifuge, see Fig. 2), and used to controlthe temperature if the unit lacks an automatic temperaturecontrol. Some designs require outlet
18、choking as well.6.1.4 Centrifuge Tubes made of transparent material, ca-pable of withstanding a G value of 36 000 for 100 h minimum(Note 1).NOTE 1Polypropylene tubes were found to be the most durable.6.2 Balance, having a capacity of about 100 g with aminimum sensitivity of 0.1 g.7. Sampling7.1 The
19、sample presented for analysis should be largeenough to make possible the selection of a representativeportion for testing. Each run will require approximately 0.5 gfor each cubic centimetre of tube capacity . Examine for anyindication of non-homogeneity such as oil separation, phasechanges, or gross
20、 contamination. If any abnormal conditionsare found, obtain a new sample.7.2 The sample temperature at time of loading is to bebetween 15C and 35C.8. Preparation of Apparatus8.1 Inspect the centrifuge unit paying particular attention tothe cleanliness of the rotor which will be unbalanced by anysurf
21、ace deposits.8.2 Examine the required number of tubes to be used for thetest, rejecting any with surface scratches or imperfections.9. Procedure9.1 For each grease, two centrifuge tubes are required. Newtubes must be used for each test and they must be handled withcare to avoid scratches.9.1.1 Deter
22、mine the total volume, V, in cubic centimetres, ofeach tube by filling with water and then pouring into agraduated cylinder and measuring.9.1.2 Measure the inside diameter, d, in millimetres with avernier caliper.9.2 Take grease samples from the container without includ-ing any free oil found on the
23、 grease surface.9.3 Charge each tube with approximately 0.5 g of grease foreach cubic centimeter of tube capacity (example:7gofgreasein a tube of 14 cm3) taking care that the difference in mass ofeach does not exceed 0.3 g to minimize centrifuge imbalance.9.4 Place the tubes in diametrically opposit
24、e compartmentsif all rotor compartments are not used. Always use evennumbers of tubes.9.5 The centrifuge lid must always be closed when the rotoris turning. The rotor should never be touched while rotating.9.6 Operate the centrifuge at a G value of 1000 for 3 min toeliminate any trapped air bubbles
25、in the grease charge.9.7 Measure the distance, a, in millimetres from the top ofthe test tube to the closest point on the grease surface as shownin Fig. 3, and calculate the grease volume as in 10.1.9.8 Replace the tubes in the rotor head, close the lid, andbring the speed up to a relative accelerat
26、ion, G, of 36 000.Consult manufacturers instructions for proper speed.9.9 At the end of the test interval, the rotor must come to acomplete stop before opening the lid.9.10 Measure the amount of oil separated as follows:3Detailed discussion is found in Calistrat, M. M., Grease Separation underCentri
27、fugal Forces, ASME Paper 75-PTG-3. Presented at the Joint ASLE-ASMELubrication Conference, Oct. 2123, 1975.FIG. 1 Installation of Dial Thermometer (Sorvall Centrifuge)FIG. 2 Choking Air Inlet of Chamber (Sorvall Centrifuge)D 4425 97 (2002)29.10.1 Cover the mouth of the tube with a piece of hardrubbe
28、r or plastic material and invert for 1 to 2 min or until allthe oil flows to the top of the tube.9.10.2 Measure the height, b, of the separated oil in milli-metres, as shown in Fig. 4.9.11 Calculate the oil volume as indicated in 10.2.9.12 Calculate the percent of oil separated from the greaseas ind
29、icated in 10.3.9.13 If the test is to be continued, return the tubes to theirrespective compartments in the centrifuge rotor. When thecovering over the tube mouth is removed all adhering oil mustbe returned to the tubes.9.14 Measure the amount of oil separation after one or moreof the following time
30、 periods: 6, 12, 24, 48, or 96 cumulativehours of testing at a G value of 36 000. No more than 72 h ofinterruption is acceptable between two test periods.9.15 The normal duration of a test is 24 cumulative hours.9.15.1 The test can be extended to 48 or 96 h if desired, butspecial reporting condition
31、s prevail (see 11.4.2).10. Calculation10.1 Calculate the grease volume to the nearest cm3asfollows:Vg5 Vt2FSa 1d2 tan AD0.785 d2! 3 103G(3)where:Vg= grease volume, cm3,Vt= tube volume, cm3(see 9.1.1),a = distance to grease surface, mm (see 9.7),d = tube inside diameter, mm (see 9.1.2), andA = angle
32、of the rotor, in degrees. This angle is specifiedby the rotor manufacturer.410.2 Calculate the oil volume to the nearest cm3as follows:Vo5 0.785 d2b 3 103(4)where:Vo= separated oil volume, cm3, andb = height of the separated oil, mm (see 9.10).10.3 Calculate the amount of oil separated from the grea
33、seto the nearest percent as follows:V 5VoVg3 100 (5)whereV = oil separation, in volume percent.11. Report11.1 The amount of oil separated from a lubricating greasesubjected to centrifugal forces is a function of the G level, theamount of time under test,2and the test temperature. Thus, toevaluate th
34、e resistance of a grease to separate the oil, thefollowing data are required:11.1.1 The oil separation, in volume percent (see 10.3).11.1.2 The level of centrifugal acceleration, in G (see 3.1).11.1.3 The duration of the test, in hours.11.1.4 The test temperature, in Celsius.11.2 In order to simplif
35、y the testing and reporting of the oilseparation from lubricating greases by centrifuging, the levelof centrifugal acceleration and the test temperature are main-tained constant, at a G value of 36 000 and 50C. Hence, theresistance of a grease to separate the oil under centrifugalforces is reported
36、as the fraction K36.K36 5 V/H (6)where:V = oil separation, in volume percent (see 10.3), andH = accumulated time of testing in hours (see 9.13).The fraction K36 should not be reduced, and the values ofboth V and H should be reported.11.3 The results of two tubes filled with the same grease(see 9.3)
37、are averaged for reporting purposes.11.4 The values for V and H in Eq 6 are those at the time theoil separation stabilizes. This is defined as the time at which theoil separation increases by less than 10 % between twoconsecutive readings.11.4.1 If the oil separation does not stabilize before the 24
38、 htest, the 24 h test results are used for reporting.4Supporting data are available from ASTM International Headquarters: RequestRR:D02-1185.FIG. 3 Measuring Grease VolumeFIG. 4 Measuring Separated OilD 4425 97 (2002)311.4.2 If the testing is extended beyond the 24 cumulativehours, the same conditio
39、ns in 11.4 apply, except more than 24h can be used. Examples of calculations can be found inAppendix X1.12. Precision and Bias412.1 PrecisionWhen run under the conditioins stated inthe test method, the precision, as determined by statisticalexamination of interlaboratory results is as follows:12.1.1
40、 RepeatabilityThe difference between successivetest results, obtained by the same operator with the sameapparatus under constant operating conditions on identical testmaterial, would in the long run, in the normal and correctoperation of the test method, exceed 4.8 percentage points (ofthe value of
41、V, 10.3) only in one case in twenty.12.1.2 ReproducibilityThe difference between two singleand independent results, obtained by different laboratories onidentical test material, would in the long run, in the normal andcorrect operation of test method, exceed 18.7 percentage points(of the value V, 10
42、.3) only in one case in twenty.12.2 BiasThe procedure in this test method has no biasbecause the value of K36 can be defined only in terms of thetest method.13. Keywords13.1 centrifuge; grease; lubricating grease; oil separationAPPENDIX(Nonmandatory Information)X1. EXAMPLES OF CALCULATIONSX1.1 Examp
43、les for 24 h Tests:X1.1.1 Cumulative hours, H 61224Oil separation, V 30 32 32K36 = 30/6, because V increased by less than 10 % betweenthe 6 and 12 h tests.X1.1.2 Cumulative hours, H 61224Oil separation, V 30 35 38K36 = 35/12, because V increased by 17 % between the 6 hand 12 h test, but only 8.5 % b
44、etween the 12 and 24 h tests.X1.1.3 Cumulative hours, H 61224Oil separation, V 30 35 42K36 = 42/24, because the oil separation did not stabilizebefore the 24 h test.X1.2 Examples for Tests Exceeding 24 h:X1.2.1 Cumulative hours, H 612244896Oil separation, V 30 35 42 44 44K36 = 42/24, because V incre
45、ased by less than 10% betweenthe 24 h and 48 h tests.X1.2.2 Cumulative hours, H 612244896Oil separation, V 30 35 42 47 48K36 = 47/48, because V increased by less than 10% betweenthe 48 h and 96 h tests.X1.2.3 Cumulative hours, H 612244896Oil separation, V 30 35 42 47 53K36 = 53/96, because the oil s
46、eparation did not stabilize beforethe 96 h test.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights,
47、 and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for rev
48、ision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you
49、 shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 4425 97 (2002)4
